In a first respect, the invention relates to methods for controlling dust and effecting soil stabilization. In a second respect, the present invention relates to the disposal of waste water.
Wind erosion of soil is a significant problem throughout the world. Due to small particle size and poor cohesion, finely divided soil is sensitive to the influence of wind. Such finely divided soil is found in agricultural lands, dunes, lake beds, construction sites and roads under construction. Erosion by wind causes the drifting of masses of soil in the form of dust. The erosion by wind causes the inconvenience of dust formation and the loss of valuable matter such as seed, fertilizer and plantlets. Dust storms are a danger to traffic and a health risk to persons residing in the vicinity.
Moreover, the effects of wind erosion on soil can be enhanced by the influence of the sun and rain. The sun causes the evaporization of moisture from soil thereby reducing the cohesion of finely divided soil. Erosion of the soil by rain is caused by rain washing away soil. This is a particular problem when agricultural soil is washed away, damaging plant life and making the soil unusable for agricultural purposes. Further, due to the influence of erosion by rain, the unprotected slopes of ditches, channels, dunes and roads may collapse or be washed away.
Therefore, it is extremely important to prevent the effects of the sun, wind and water in eroding soil. It has been proposed to prevent the shift, drift and erosion of soil by treating the surface layers of the soil with water dispersible high polymeric substances of a natural or synthetic nature. Examples of these high polymeric substances include starch ethers, hydrolyze polyacrylonitril, polyvinyl alcohol and carboxymethyl cellulose. U.S. Pat. No. 3,077,054 discloses the use of polyvinyl acetate as an anti-erosion agent. U.S. Pat. No. 3,224,867 teaches the conditioning of soil with mono starch phosphate. U.S. Pat. No. 5,125,770 teaches treating the soil with a pre-gelatinized starch and a surfactant compound. Furthermore, it has been known to treat dirt roads with relatively pure solid sodium chloride (NaCl), calcium chloride (CaCl.sub.2), and mixtures of the two.
There are several drawbacks with the aforementioned soil treating compounds. The polymers mentioned have a relatively high price and have potentially harmful environmental properties. In addition, the starch ethers have proved sensitive to washing out by rain water. As a result, their effectiveness as an anti-erosion agent is severely limited.
Furthermore, it would be highly desirable to provide a method for treating soil that is of low cost and utilizes a material or compound which is readily available.
Accordingly, it would be highly desirable to provide a method for treating soil to control dust and effect soil stabilization. As used herein, soil stabilization refers to the treatment of soils with chemicals to offset the tendencies of soils to be sensitive to small changes in the types of ions in the soil moisture as they effect the plasticity of the soil. For example, swelled clays, those with layers of "bound" water molecules, are more susceptible to movement under load. Soil stabilization of swelled clays can be effected by altering the types and/or amounts of ions in the soil mixture.
An additional problem encountered throughout the world involves the disposal of waste water. The softening of hard water by the removal of calcium and magnesium is required for both industrial and household use. Known water softening processes proceed either by way of ion-exchange, membrane softening or precipitation. In the ion-exchange processes, the calcium (Ca.sup.2+) and magnesium (Mg.sup.2+) ions are exchanged for sodium (Na.sup.+) and regeneration of the ion-exchange resin is achieved with a large excess of NaCl. This process creates a regeneration effluent being a relatively concentrated aqueous solution of sodium, calcium and magnesium chlorides which has to be discarded. Consequently, by this method, considerable amounts of sodium, calcium and magnesium salts in solution must be disposed of.
Alternatively, it is possible to use weak acid resins which exchange hydrogen (H.sup.+) for calcium (Ca.sup.2+,) and magnesium (Mg.sup.2-), and to regenerate the spent resins with a mineral acid. While this method creates less waste water, it is more expensive and yields relatively acidic soft water which is corrosive. Meanwhile, membrane softening concentrates the calcium, magnesium salts and salts of other divalent ions to produce waste waters which require costly disposal.
The precipitation process has traditionally been carried out by the "lime soda" process in which lime is added to hard water to convert water soluble calcium bicarbonate into water insoluble calcium carbonate. This process also results in waste water which is difficult to filter and requires cumbersome treatment.
My previously issued patent, U.S. Pat. No. 5,300,123 (which is incorporated herein by reference), relates to the purification of impure solid salts. Even this process produces salty waste water which must be disposed of.
The disposal of waste water has become an expensive problem for society. For example, approximately 1.61 billion gallons of waste water containing approximately 800,000 tons of mixed sodium, calcium and magnesium chlorides and sulfates is produced from water treatment operations and oil fields in the State of California alone. This waste water must be disposed of, costing millions of dollars.
Accordingly, it would be highly advantageous to provide an improved method of disposing of salty waste waters. It would even be more advantageous to provide a method of disposing of salty waste waters which provides a benefit to society. It would be even more advantageous if salty waste waters could be used to treat soil to control dust and effect soil stabilization.